This application relates to the art of tires and, more particularly, to tire treads. The invention is particularly applicable for use with tires that are designed for off-road use and will be described with specific reference thereto. However, it will be appreciated that the invention has broader aspects and that features of the invention may be used on tires that are designed for other purposes.
Vehicles being driven in off-road terrain often become stuck in ruts or among large rocks because the tires loose traction and/or support. Tire sidewalls usually have inadequate traction and/or support surfaces that would allow the tire to gain traction against and/or climb the side of a rut or rock. It would be desirable to have a tire with performance characteristics providing sidewall traction and sidewall support surfaces that enable the tire sidewall to gain traction on and/or climb the sides of rocks and ruts.
In accordance with the present application, a tire tread has tread elements with sidewall extensions that extend along the tire sidewalls toward the tire rotational axis and that project outwardly from the tire sidewalls away from the tire tread centerline. A plurality of the sidewall extensions are sidewall primary extensions that have at least two steps therein radially of the tire rotational axis to provide at least two sidewall primary extension support surfaces that face away from the tire rotational axis and are spaced different distances from the tire rotational axis and from the tire tread centerline. The tread elements themselves have outer tread support surfaces that are spaced farther from the tire rotational axis than either of the primary extension support surfaces.
In one arrangement, the sidewall extensions include sidewall secondary extensions that are located intermediate the sidewall primary extensions circumferentially of each tire sidewall. The sidewall secondary extensions are smaller than the sidewall primary extensions both radially and circumferentially of the tire, and have at least one step therein to provide at least one secondary extension support surface that faces away from the tire rotational axis.
In accordance with another aspect of the application, the sidewall primary extensions have outer surfaces that intersect the tread support surfaces at primary intersections, and the sidewall secondary extensions have outer surfaces that intersect the tread support surfaces at secondary intersections. The secondary intersections are spaced outwardly from the tread centerline a greater distance than the spacing of the primary intersections from the tread centerline.
The sidewall extensions preferably have outer surfaces that extend along the tire sidewalls and have depressions therein that open outwardly in a direction away from the tread centerline.
The sidewall primary extensions preferably have opposite sides that diverge in a direction toward the tire rotational axis. This provides the primary extensions with a progressively increasing circumferential width proceeding in a direction from the tire tread surface and along the tire sidewall toward the tire rotational axis.
The sidewall secondary extensions have a constant width along the tire sidewalls in a direction circumferentially of the tire sidewalls, and the width of the sidewall secondary extensions is less than the width of the sidewall primary extensions.
In accordance with another aspect of the application, the outer surface of each tread element has an inner circumferential groove spaced a first distance outwardly from the tread centerline on one side thereof, and an outer circumferential groove therein on the opposite side of the tread centerline from the first circumferential groove and spaced outwardly from the tread centerline a second distance greater than the first distance. Alternate ones of the tread elements have the inner circumferential grooves therein located on one side of the tread centerline and the remainder of the tread elements have the inner circumferential grooves therein located on the opposite side of the tread centerline.
The tread elements have circumferential central grooves therein, and alternate ones of the tread elements have the central grooves therein located on one side of tread centerline while the remainder of the tread elements have the central grooves therein located on the opposite side of the tread centerline. One sidewall of each central groove is coincidental with the tread centerline.
A tire tread in accordance with the present application has two different tread elements that alternate around the circumference of the tire. One tread element has a sidewall primary extension at one end thereof along one sidewall and a sidewall secondary extension at the opposite end thereof along the other tire sidewall. The next adjacent tread element is reversed so that its sidewall primary extension extends along the other sidewall while its sidewall secondary extension extends along the one sidewall.
It a principal object of the present invention to provide a tire having excellent off-road traction. It is another object of the invention to provide an off-road tire with sidewalls having traction elements that enable the tire to gain traction on and/or climb the sides of rocks and ruts.
It is an additional object of the invention to provide such a tire that has self-cleaning action in mud and snow.
It is a further object of the invention to provide a tire with tread elements that extend along the tire sidewalls and have steps therein to provide sidewall support surfaces at a plurality of different distances from the tire rotational axis and from the tread centerline.